Fix typo in error message (it's -> its)

Co-authored-by: sfmskywalker <938393+sfmskywalker@users.noreply.github.com>

Author: Copilot

src/modules/Elsa.Workflows.Core/Activities/Flowchart/Activities/Flowchart.Counters.cs

@@ -180,7 +180,7 @@ private static async ValueTask<bool> MaybeScheduleOutboundActivitiesAsync(FlowGr
         // but was legitimately scheduled by another trigger
         if (flowGraph.IsDanglingActivity(activity) && outboundConnections.Count == 0)
         {
-            throw new($"Activity {activity.Id} is not reachable from the flowchart graph and has no outbound connections. Unable to schedule it's outbound activities.");
+            throw new($"Activity {activity.Id} is not reachable from the flowchart graph and has no outbound connections. Unable to schedule its outbound activities.");
         }
 
         // Register the activity as visited unless it was executed due to a backward connection